Production of maleic acid and its anhydride



Patented 0a. 4, 1932 UNITED; sTA'ras LPATENT OFFICE orro nnossnaon, onnunwIasmrEn-oN rnn-nnmn, GERMANY, assrenon. 'ro r. o.

rannmzmnusrnm nxrmnonsnnnsomrr, or pnanxronr-ox-rnn-mm, enn- MANYPRODUCTION OF HALEIG ACID AND ITS RIDE No Drawing. Application filedSeptember 12, 1931, Serial No. 562,605, and in Germany September 24,1980.

The present invention relates to improvements in the production ofmaleic acid and its anhydride. f

I have found that maleio acid and its anhydride are obtained readily andin good yields by bringing a crotonic substance corresponding to theformula 7 in which x is either -COOH hr con, i. e. crotonaldeh do orcrotonic acid, or a 1xture of bot in the vaporphase toge her withoxygen, or gases containing oxy en, into contact with catalystsconsisting o of essentially containing at least one of the oxides ofvanadium and molybdenum at temperatures between about 200 and about 500C. preferably between 250 and 380 C. I The reaction commences at ratherlow temperatures; for example even at a temperature as low as 250 C.maleic acid is obtained in good yields. Theoretically 1 molecularproportion of crotonaldehyde' requires at east 2 molecular proportionsof 0 gen, an equimolecular proportion ther'eo -being ,theoreticallysufiicient for oxidizing crotonic acid; the best results are, however,obtained when employing oxygen in alarge excess over the quantittheoretically required; the oxygen may be fluted with inert gases, such;as nitrogen or carbon dioxide. Since air is cheaper than pure oxygen, Iprefer to emplo air, and I employ generally, about 1 cubi meter of airfor irom about 20 to 56 grams, preferably about 20 grams, of cro tonicacid or crotonaldehyde- An amount from about 56 grams to about. 480grams of crotonaldehyde for 1 cubic meter of air is preferably notemployed in ordei" to avoid explosions; it however, a. quantity.ofcrotonaldehyde within the said range be employed explosions may stillbe avoided by working at a decreased pressure and at a correspondinglylower temperature. The

addition of carbon dioxide to the gaseous mixture may also .reduce therisk of explosions. A special advantage, inter alia,of the processaccording to the present invention is that very pure maleic acid freefrom'mjurious by-produete is obtained. Instead of crotonaldehyde,acetaldol, which when heated to about 84 to 85 C. is readily convertedinto croto'naldehyde, may be directly employed.

As already stated, the catalysts consist of ,or essentially contain, atleast one oxide 0 oxides such as titanic oxide and hydrated titanicoxide, tungstic oxide and its h drate, silica or alumina. Since thesediiiicu tly reducible oxides act as activators, a very small amount ofvanadium or molybdenum oxide is required, if such diluents be employed.In addition to the vanadium and/or molybdenum oxides, or to the mixturesof thesev oxides with the said diluents, small amounts of other basemetal oxides may also bepresent in the catalysts such as. for examplezinc oxide, cerium oxide, chromium oxide, cobalt oxide, lead oxide,zirconium oxide, tin oxide, potassium oxide, sodium oxide, lithiumoxide, rubidium oxide, calcium oxide, barium oxide, strontium oxide,magnesium oxide and the other base metal oxides. The said oxides mayalso be present in the catalysts in the form of their salts with thoseoxides which are of acidic nature; thus for example alkali 96 metal oralkaline earth metal vanadates or molybdates may be employed as thecatalysts and alkali metal or alkaline earth metal tungstates orsilicates may be present therein. Also natural silicates, such as pumiceor 'kieselguhr, may be employed as diluents for catalysts,-the smallamount of metallic impurities, such as calcium, magnesium, barium orstrontium oxides, contained therein, actinias activator in. many cases.

. specially active catalysts are obtainedby I employing the lower oxidesof vanadium or ybdenum (V20 V 0 and M00 as such or preferably togetherwith titanic oxide; such catalysts may be preparedvby heating to drynessaqueous dispersions of the oxides or of salts of the correspondingmetals together with an aqueous solution of oxalic acid. When porousdiluents, such as pumice, are employed, the metal oxides may e directlyfixed thereon in this way, for ex ample by heating to dryness a mixtureof granulated pumice and pulverized ammo-' nium vanadate and titanicoxide, suspended in water.

The process may be carried out under atmospheric or any desiredpressure.

The following examples will further-illustrate the nature of thisinvention but the invention is not restricted to these examples.

I Example 1 When a mixture of crotonic acid va ors,

and air obtained by passing 200 liters 0 air per hour of crotonic acidheated to 90 C. is led at 320 C. over the same catalyst, maleicanhydride is likewise formed. If aldol be em loyed the evaporation ispreferably carrie out at from 80 to 90 C. and with a current of airhaving a velocity of from to 10 liters only per hour and the vapor mix-'ture is then mixed with further quantities of air.

Example 2 A current of air is passed at a velocity of liters per hourthrough an 87 per cent crotonic aldehyde warmed to C. The

current of air laden with vapors of the -alde-- hyde is combined with, asecond current of $111 havin a velocity of 220 liters per 'hour and thew ole gaseous mixture is then passed at 300 C. over a catalyst which hasbeen prepared in the following manner: 20 gramsof molybdic' acid aresuspended in 100 cubic centimeters ofdistilled water together with 8grams of vanadic acid, 10 grams of titanium oxide and 10 grams of oxalicacid, .10

cubic centimeters of granulated pumice (having a diameter of thegranules of about the size of peas) then being added and the wholeevaporated to dryness while stirring. The gaseous mixture leaving thereaction chamher is cooled and washed with water, whereby from 105 to 110 parts ofmaleicacid are obtained from each 100 parts of crotonicaldehyde calculated as 100 per cent aldehyde,

about 80 per cent of the acid being in the form of its anhydride.

- Ewample 3 7 A current of air is led at a speed of 200 liters per hourthrough crotonaldehyde at a temperature of 0 C. The current of air ladenwith vapor of the aldehyde is passed at 400 C. over a catalystconsisting of an intimate mixture of; kieselguhr, pot ssium sulphate andvanadid acid. The maleic acid contained in the mixture leaving thereaction chamber is obtained by cooling the mixture and washing withwater.

Example 4 A current of air is passed at a velocity of 150 liters per'our through an 87 per cent crotonaldehyde cooled to 0 C. The gaseousmixture is then assed at 310 over a catalyst obtained y impregnating 100cubic centimeters of granulated pumice (the granules of which have adiameter of, about ,the size'of peas) with a,suspension of 20 grams oftitanic oxide, 5 grams of ammonium molybdate and 3 grams of oxalic acidin 100 cubic centimeters of distilled water, and dry-1 ing. The maleicacid contained in the gaseous mixture leaving the catalyst is-obtainedin a yield.of parts for each 100 parts of crotonic aldehyde caltulatedas 100 per cent aldehyde, by cooling and washing the mixture.

Ewample 5 A current of air is passed at a velocity of 200 liters perhour over fused crotonic acid at 90 C. The resulting mixture of air andvapors of crotonic acid is then contacted. at 280 C. with a catalystobtained by impregnating 100 cubic centimeters of granulated pumice (thegranules of which have a diameter of about the size of peas) with a susension of 11 grams of ammonium molyb ate, 3.2 "gramsof vanadic acid, 4parts of titanic anhydride'and 4 grams of oxalic acid in 100 cubiccentimeters of water, and drying. Crystals of pure maleic anhydrideareobtained by cooling the gaseous mixture which has\ passed over thecatalyst; in order to recuperate the whole of the maleic anhydrideformed, the cooled gases are washed-with water.

Example 6 A current of air is passed at a velocity of 2 liters per hourover acetaldol heated to 85 C. The resultin mixture of air with vaporsof crotonaldehy de and water is dried by means of calcined sodiumcarbonate, combined with a second current of air having a velocity of200 liters per hour and passed tained by washing with water the gaseousmixture leaving the reaction chamber and eva crating the aqueoussolution. at I claim is 1. The process for the production of maleic acidand maleic anhydride which comprises contacting vaporous non-explosivemixtures of oxygen and crctonic substances corresponding to the formulaCH CH= CH X,

wherein X is -COOH or -COH, with a catalyst essentially comprising atleast one oxide of the metals vanadium and molybdenum at a tem eraturebetween about200 and about tially comprising at least one oxide ofthemetals vanadium and molybdenum at a temperature between about 200 andabout 3. The process for the production of maleic acid and maleicanhydrlde which comprises contacting a vaporous mixture of 1 cubic meterof air and from about 20 to about 56 grams of crctonic substancescorresponding to the formula CH CH=CH X, wherein X is -COOH or -COH,with a catalyst essentially comprising at least one oxide of the metalsvanadium and molybdenum at a temperature between about 200 and about 500C.

4. The process for the production of maleic acid and maleic anhydridewhich comprises contacting vaporous non-explosive mixtures of oxygen andcrctonic substances corresponding to the formula CH CH= OH X, wherein X-is -COOH or -COH, with a catalyst essentially comprising vanadium oxideat a temperature between about 200 and about 500 C.

' 5. The process for the production of maleic 'acid and maleic anhydridewhich comprises contacting vaporous non-explosive'mixtures of oxygen andcrotonlc substances correspondingto the formula CH OH CH X,

wherein X is -COOH or -COH, with a cata-' lyst essentiallycomprisingmolybdenum oxide at a tem era'ture between about 200 and about500 6. Theprocess for the production of maleic acid and maleic anhydride whichcomprises contacting vaporous non-explosive nixtures of 0 gen andcrctonic substances corre' spondm to the for ulaCH r- CH =CHX, whereinis -COO or -COH, with a catalyst essentially comprising at leastone'o'xide of the metals vanadium and molybdenum anda solid diluent at atemperature between about 200 and about 500 0. i

. 12. The process for the 7. The process for the production'of maleic ofoxygen and crctonic substances corresponding to the formula CH CH= CH X,wherein X is --GOOH or -COH, with a catalyst essentially comprising atleast one oxide of the metals vanadium and molybdenum deposited ongranulated aluminium at a tem-v perature I between about 200 and about500 C.

8.The process for the production of maleic acidand maleic anhy, ridewhich comprises contacting vaporous n-explosive mixtures of oxygen andcrctonic substances corresponding to the formula CH CH= CH X, wherein Xis 60011 or -COH, with a catalyst essentially comprising at least oneoxide of the metals vanadium and molybdenum and a solid diluentcomprising a metal compound, difiicultly reduc ble by hydrogen to thecorresponding metal, at a temperature between about 200 and about 500 C.

"9. The process for the production of maleic acid and maleic anhyda'idewhibhcomprises contacting vaporous non-explosive mixtures of oxygen andcrctonic substances corresponding to the formula CH1 CH CH X, wherein Xis -GOQH or -COH, with a catalyst essentially comprising at least oneoxide of the metals vanadium and molybdenum and a diluent of a metaloxide, diificultlyreducible by hydrogen to thelcorresponding metal, at atemperature bet een about 200 and about 500 C.

10. The process for the production of maleic acid and maleic .anhydridewhich comprises oontacting vaporous non-explosive mixtures of oxygen andcrctonic substances corresponding to the formula CH .CH=CHX, wherein Xis -COOH or -COH, with a catalyst essentially comprising at least oneoxide of the metals vanadium and molybdenum and titanium oxide, atatemperature between about 200 and about 500 C.

11.. The process for the production of 'wherein -COOH or -COH,' with acatalyst, essentially comprising at least one oxide of the metalsvanadium and mol bdenum and'alumina, at a temperature etween about 200and about 500 C.

production of maleicfacid and maleic anhydrlde which comprisescontacting vaporous mixtures of oxygen with substances corregponding tothe ormula CH -()"l lI=('lH--- wherein X is v COOH or COH, with acatalyst essentially comprising a. lower oxide of the metals vanadiumand molybdenum and .a tltamum' oxide at a temperaturebetween about 200and about 500 .C. a

13. The process for the production of maleic acid and maleic anhydridewhich comprises contacting vaporous mixtures of oxygen and crotonic acidwith a catalyst ssentlally comprising at least one oxide of the meta1svanadium and molybdenum at a tempjerature between about 250 and about380.

14. The process for the production of maleic acid and maleic anhydridewhich comprises contacting .vaporous non-ex losive mixtures of oxygenand crotonaldehy e with a catalyst essentlally comprising at least oneoxide of the metals vanadium and molybdenum at a temperature betweenabout 250 and about 380 C v 15. The process for the production of maleicacid and maleic anhydride which comprises contacting 'vaporousnon-explosive mixtures of 7 oxygen and .crontonaldehyde with atcatalystcomprising at least one oxide.

of the metals vanadium and molybdenum and titanium oxide and pumicebetween about 250 and 380 C.

16. The process for the production of maleic acid and maleic anhydridewhich comprises contacting vaporous mixtures of oxygen and crotonic acidwith a catalyst com- I prising molybdic oxide, vanadic oxide, titanium'oxide and pumice at about 280 C.

Intestimony whereof I have hereunto set my hand.

OTTO DROSSBACH.

